Material for and process of coating metal



Patented Jan. 24, 1933 UNITED v STATES P TENT caries Jansen. GRAVELL, or ELKINS- mum,- rmmsnv'anm, Assmnon 'ro matron:

CHEMICAL PAINT COMPANY, OF AMIBLER, PENNSYLVANIA, A CORPORATION OF DELAWARE No Drawing.

This invention relatesto the art of coating metal and is particularly directed to prevent-- I such as hand marks, acid runs, oil, etc., as

' experience has shown that such materials soon v in the said solvent and a metal etching acid cause the development of defects in the final finish. But even when this is done, failures still occur. f

The objects of this invention are to provide a coating where less care has to be exercised to rid the metal of this extraneous ma'tter; to provide a coating of longer life; to reduce the'number of operations necessary to properly finish metal; to reduce the cost of coatingmetal and to generally improve theart ofpreventing metal from corroding.

I have discovered that if a metaletching acid is addedto the waterproof material used for coating the metal, a great benefit results, in that the coating holds much bet ter to the metal and hence acts as a better protector. As simple mechanical mixtures of the acid and the waterproof-coating material do not always seem to produce uniform results, it is necessary to properly'design the coating material so that the said acid isac-T tually dissolved and held in solution by the water-proof coating material itself.

To do this I provide an admixture comprising a solvent, a Water-proof material soluble soluble in. the water-proof material but not soluble in the said solvent. By dissolving the acid in the water-proof material and not'in the solvent it is evident that the acid remains uniformly distributed in-the resultant coating after the solvent has evaporated, thus producing a new type of coating comprising a consolute solution of a water-proof material and a metal etching acid.

' The solvent used inmy admixture may be any suitable hydrocarbon capable of dissolv-' ing the water-proof material selected, such hydrocarbons as benzole, naphtha, petroleum Application filed March 4,

1930. Serial No. 433,187. A

of what is known in the tradeas solvent naphtha, coal tar solvent, or industrial xylol, and kerosene. 5

The water-proof material may be any suitable, material soluble in the solvent and capable of dissolving a metal etching acid; certain resins, fatty acids, tars and pitches have this property. It is especially marked in the case of stearine pitch and I prefer to use it in my practical material.

spirits or kerosene. I prefer .an admixture The acid selected should be soluble in the water-proof material but not soluble in the solvent used. The best results are obtained with orthophosphoric acid. This is soluble in the pitch, but it is insoluble in the solvent used for dissolving the pitch. I find there is' an advantage in drying my coating at atem' perature sufiiciently high to decompose the phosphoric acid into the pyro or the meta acid and thus make it less liable to be leached out of the resultant coating by exposure to water. As it is safe to dry my coating at a temperature of 232 centigrade and as ortho- Orthophosphoric acid (100%)@ 10 pounds The pitch is dissolved in the admixture of the naphtha and kerosene and the acid made liquid byv heating, added slowly whilestir- The material thus produced has properties similar to a varnish and for certain uses may, on drying onthe metal, be too;transparent or too smooth. The cellulose lacquers for instance. will not adhere properly to such a smooth surface and when these finishes are to be applied over my coating. it is wellto add a filler to the above material that tends to give a tooth to my coating. and this offer. points 'of attachment for the lacquer. Fillers such clay or silica may be'employed for this purpose; that form of silica known as fossil meal produces very satisfactory results. About 225 pounds of this added to the above admixture gives suificient roughness for securing a tight coating of cellulose lacquer.

Where it is desired to give my coating more hiding powers or when a colored coating is wanted, various pigments may be used as the filler. Chrome green oxide gives my coating a green color and lamp-black may be used for the metal to a thin film. The metal is then dried; after which it is ready to receive my coating. The coating is best applled by dipping although it may be applied by hrus ing or spraying if desired. The coated metal is then allowed to drain for ten minutes, more or less, and then placed in an" oven heated' to approximately 232 centigrade where it is allowed to remain for about a half an hour. On removing it from the oven, 1t'

will be found that the coating has become hard and dry yet possessing a ductlllty WhlCll enables it to stand much bending and drawldoth salt spray and the humidity cabinet tests indicate the superiorityof my coating over that of the prior art in that the life of my'finish is longer and corrosionoccurring where the finish is scratched through to the metal, confines itself to the scratched portion and does not extend further and further under the finish as time goes on, as would be the case where the usual finish is used. As my coating has superior powers to resist corrosion, it is not necessary to use as many coats to get the desired weather proofing effect where my coating is used as the priming coat; one coat of my material and one top coat often ofiers more protection against the weather than three or more coats of the materials used priorto my invention.

I claim: 1

1. A material for coating metal, being an admixture comprising kerosene, stearine pitch and orthophosphoric acid.

2. A material for coating metal, being an admixture comprising kerosene, stearine pitch, orthophosphoric acid and lamp-black.

3. A material for coating metal being an admixture comprising waterproof material and tri-hydric anhydrous metal etching acid, said material and acid being in solution with respect to each other, and said admixture also comprisin a volatile thinner in which the first name solution is dissolved and which isincapable .of dissolving the acid alone, whereby, when the thinner volatilizes, the

acid and material remain mutually dissolved. I

4. Amaterial for coating metal bein an admixture comprising stearine pitch an trihydric anhydrous metal etching acid, said pitch and acid'being in solution with respect to each other, and said admixture also com-. prising a volatile thinner in which the first named solution is dissolved and which is incapable of dissolving the acid alone, whereby when the thinner volatilizes the acid and pitch remain mutually dissolved.

5. A material for coating metal being an admixture comprising waterproof material and orthophosphoric acid, said material and acid being in solution with respect to each other, and said admixture also comprisin a volatile thinner in which the first named so ution is dissolved and which isinc'apable of dissolving the acid alone, whereby w en the thinner volatilizes, the acid and material remain mutually dissolved.

6. A material for coating metal'being an admixture comprising stearine pitch and orthophosphoric acid, said pitch and acid being in solution with respect to each other, and said admixture also comprising a volatile hydrocarbon thinner in which the first named solution is dissolved and-which isincapable ofdissolving the acid alone, whereby when the thinner volatili'zes, the acid and stearine pitch remain mutually dissolved.

7. The process of coating metal with a hard, dry, ductile and adherent coating comprising waterproof material and at metal etching acid uniformly distributed throughout the coating material, which consistsinto clean metal a fluid admixture.

applying comprising waterproof material and 'i-trihydric anhydrous metal etching acid in solution with respectto each other and also comprising a volatile thinner in which the first named solution is dissolved and which is in-.

capable of dissolving the acid alone, and volatilizing the thinner and drying the mutually dissolved acid and coating material by heatin the metal.

8. T e process of coating metal with a hard dry ductile and adherent coating comprising waterproof material and metal etching acid uniformly distributed throughout the coating material, which consists in applying to clean metal a fluid admixture comprising stearine pitch and orthophosphoric acid in solution with respect to each other and also comprising a volatile thinner in which the first named solution is dissolved and which is incapable .ofdissolvingthe acid alone, and volatilizing the thinner and drying the mutually dissolved acid and pitch by heating the metal.

JAMES H. GRAVELL. 

